Renal Stones A Guide for the Non-Urologist.ppt

Renal Stones: A Guide for the Non-Urologist F. A. Fried, MD University of North Carolina Division of Urology Pathogenesis of Renal Stones all urinary stones are composed of 98% crystalline material and 2% mucoprotein the crystalline component(s) may be found “pure” or in combination with each other. the common characteristic that all crystalline components share, is that they have a very limited solubility in urine Pathogenesis of Renal Stones (cont.) 99% of renal stones (in western hemisphere) are composed of: calcium oxalate 75% (mono or di hydrate) calcium hydroxyl phosphate (15%)(apatite) magnesium ammonium phosphate 10% (struvite) uric acid 5% cystine 1% Pathogenesis of Renal Stones (cont.) investigations show that the formation of a stone is similar to the development of a crystalline mass in vitro given that stone formation is an example of crystallization one could predict: the necessity for a supersaturated state in urine the occurrence of spontaneous crystallization the need for the earliest polycrystalline state to be arrested in the u.t. allowing time for growth Spontaneous Crystallization normal urine has crystals (at times) normal urine is extremely effective in maintaining a stable supersaturated state there are certain components of urine that enhance ability to maintain ss state inhibit development of crystals Site of Stone Development Question: Where in the UT does urine reach its maximal concentration while still in a microscopic sized lumen so that crystalline particles that may form can get “stuck” in the lumen? Answer: The collecting duct which runs through the renal papilla. Any part of the UT distal to this point has a large lumen and small particles would easily pass. Clinical Risk Factors occupation family history diet hydration small bowel disease (i.b.d.) medical conditions causing hypercalcuria medical conditions causing aciduria Clinical Features acute obstruction of ureter---severe colic flank pain referred to genitalia naus